[cfe-commits] [PATCH] Parsing C++0x lambda expressions

[Sean Hunt]

On 07/06/11 14:00, John Freeman wrote:
>> +  bool first = true;
>> +  while (Tok.isNot(tok::r_square)) {
>> +    if (first) {
>> +      first = false;
>> +
>> +      // Parse capture-default.
>> +      if (Tok.is(tok::amp)&&   NextToken().isNot(tok::identifier)) {
>> +        List.Default = DEFAULT_CAPTURE_BY_REF;
>> +      } else if (Tok.is(tok::equal)) {
>> +        List.Default = DEFAULT_CAPTURE_BY_COPY;
>> +      }
>> +
>> +      if (List.Default != DEFAULT_CAPTURE_NONE) {
>> +        // Consume '&' or '='.
>> +        ConsumeToken();
>> +        continue;
>> +      }
>> +    } else {
>> +      if (ExpectAndConsume(tok::comma,
>> +                           diag::err_expected_comma,
>> +                           "",
>> +                           tok::r_square)) {
>> +        // FIXME: We could also expect end of capture list. Should the
>> +        // diagnostic indicate this?
>> +        return ExprError();
>> +      }
>> +    }
>>
>> I find this logic to be a bit twisty. Why not do an initial check for&   (followed by non-identifier) or = to set the default capture kind, then go into the loop that handles individual captures?
>
> I believe it will still require some twisty logic. What will the loop
> handle? If it succeeds on an empty list, then we will need special logic
> if the default is followed by a comma but no capture past that. If it
> succeeds only on a non-empty list, then we will need special logic for
> an empty list. I thought this was the best solution.
>
> - John

Pseudo-code:
  if (is('=' or '&') and next token is not identifier)
    set default capture
    if (is(','))
      consume comma

  loop()

Sean